The present disclosure relates to an inverter system, and more particularly, to a method of detecting a state of a power cable in an inverter system capable of detecting the state of the power cable and forcibly discharging residual energy in a direct current (DC)-link capacitor when a disconnection occurs.
Inverter systems are electric/electronic sub assemblies (ESAs) converting a high voltage direct current (DC) power into an alternating current (AC) or a DC power and are primary components included in electric motors of vehicles.
Motors applied as driving units to echo-friendly vehicles are driven by phase currents transferred through a first high voltage power cable from an inverter converting a DC current into a three-phase voltage according to a pulse width modulation (PWM) signal of a controller.
Also, the inverter converts a DC link voltage transferred through a second high voltage power cable by opening and closing of a main relay into a three-phase voltage.
Accordingly, when any one of the first power cable connecting the inverter to the motor and the second power cable connecting a high voltage battery to the inverter is separated, the motor is not smoothly driven and a high voltage/high current is left to an inverter system, thereby causing a fatal error damaging the entire inverter system.
FIG. 1 is a diagram of a general apparatus for detecting a separation of a power cable in an inverter system.
Referring to FIG. 1, the apparatus includes a power cable 10, a connector 20, and a sensor 30 formed between the power cable 10 and the connector 20 and transmitting a signal according to a separation between the power cable 10 and the connector 20.
The sensor 30 is connected to a contact portion between the power cable 10 and the connector 20 and transmits a digital signal to a controller according to whether the power cable 10 is connected to the connector 20.
That is, in general, a sensor for checking whether the power cable 10 is separated is additionally installed in an aspect of hardware in one of the power cable 10 and the connector 20. It is checked using a digital signal outputted from the sensor in real time whether the power cable 10 is separated.
However, since the apparatus for detecting the separation of the power cable only detects whether the power cable is separated in the aspect of hardware, there are limitations in price and space.
Also, the apparatus for detecting the separation of the power cable may easily misoperate due to an external cause such as vibrations, etc., which causes a danger in safety of a driver.
In an inverter system for an electric automobile, when a power cable is disconnected or a connector is unfastened due to vibrations and external causes while driving or stopping, it is impossible to check a state of a high voltage cable or an electric contact point is exposed to make the state unstable, which includes dangers. Accordingly, it is necessary to safely stop a vehicle by rapidly detecting the disconnection and unfastening.
Also, when the power cable is disconnected and the connector is unfastened, a worker or a driver accesses the vehicle while a DC-link capacitor is being charged, which leads to a big accident.